The properties of chromium oxide coatings on NdFeB magnets by magnetron sputtering with ion beam assisted deposition

• Cr2O3 coatings are first used on sintered NdFeB magnets by magnetron sputtering.
• Cr2O3 coating by IBAD has excellent properties due to crystal structure obtained.
• Effect of oxygen flux on microstructure and properties is discussed.

The coatings of Cr2O3 were deposited on sintered NdFeB magnets by direct current (DC) pulse magnetron sputtering with and without ion beam at different O2 pressures. The coatings were compact and had a thickness of 1.8–2.2 μm. The coatings achieved a hardness up to 29 GPa and a wear rate of 1.78 × 10−7 mm3/Nm when ion-beam-assisted-deposition (IBAD) was used. Excellent anti-corrosion properties were obtained in the coating prepared by IBAD while the good magnetic properties of NdFeB substrate were retained. Electrochemical measurements revealed that the corrosion current density of the sample decreased from 4.66 × 10−6 A/cm2 (bare NdFeB) to 2.87 × 10−7 A/cm2 when O2 flux was 17 sccm during IBAD process.